Lumber Processing inLumber Processing in Selected Sawmills in Durango and Oaxaca, Mexico 3 logs are pine species, with a small percentage of oak. We saw no effort to separate the various

Lumber Processing in Selected Sawmillsin Durango and Oaxaca, MexicoRoland HernandezMichael C. Wiemann

United StatesDepartment ofAgriculture

Forest Service

ForestProductsLaboratory

GeneralTechnical ReportFPL–GTR–167

May 2006

Hernandez, Roland; Wiemann, Michael C. 2006. Lumber processing in selected sawmills in Durango and Oaxaca, Mexico. General Technical Report FPL-GTR-167. Madison, WI: U.S. Department of Agriculture, For-est Service, Forest Products Laboratory. 14 p.

A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53726–2398. This publication is also available online at www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries in the United States and elsewhere.

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin.

The use of trade or firm names in this publication is for reader information and does not imply endorsement by the United States Department of Agriculture (USDA) of any product or service.

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Abstract

This report documents a technical assistance trip to four community-owned forests and associated sawmill and secondary processing operations in the vicinities of Durango and Oaxaca, Mexico. The products and processes of these enterprises are described, and recommendations for im-provement are provided.

Keywords: Ejido, bosque comunal, sawmill, Durango, Oaxaca, Mexico, Pinus, Quercus

ContentsPage

Introduction ......................................................................... 1Description of Sawmills ...................................................... 1 Logs ................................................................................. 1 Log Sorting ................................................................. 3 Log Breakdown ........................................................... 3 Slab Recovery ............................................................. 5 Grading ....................................................................... 5 Kiln-Drying ................................................................. 7 Finished Products ............................................................ 7Information Gathered .......................................................... 9 Comparison of Mexican and U.S. Pines ......................... 9 Comparison of Mexican and U.S. Oaks .......................... 9Comments and Recommendations .....................................10Trade Associations .............................................................11Literature Cited ..................................................................11Appendix—Uses For Low-Grade Lumber ........................12

Lumber Processing in Selected Sawmillsin Durango and Oaxaca, MexicoRoland Hernandez, Research EngineerMichael C. Wiemann, BotanistForest Products Laboratory, Madison, Wisconsin

IntroductionThe Forest Products Laboratory (FPL) was contacted by the USDA Forest Service International Programs to provide technical assistance to sawmills in Durango and Oaxaca, Mexico. A technical visit was coordinated with members of the Rainforest Alliance.

In Mexico, forests (bosques) are primarily community-owned. There are two categories of community-owned forests, “bosques ejidales” (also known as “ejidos”) and “bosques comunales.” The main difference between these two systems is in land tenure. Ejidos may be subdivided into parcels with individual owners, although a family may not own more than one parcel. Bosques comunales, on the other hand, may not be subdivided, although the total number of owners can increase.

Communities use their collective forest holdings to supply timber industries. Much of the production supplies local markets, but there is increasing interest in export markets as a source of foreign exchange. Foreign markets are demand-ing, and high quality is required by importers of timber and timber products. We visited timber production industries associated with community forests to familiarize ourselves with their current operations and lumber grading methods, and to survey the various species that are harvested. The for-ests that we visited produce mostly pine, with small quanti-ties of oak. The regions we visited are shown in Figure 1.

Description of Sawmills We visited four sawmills approximately 2 to 4 h driving time from the metropolitan areas of Durango and Oaxaca, Mexico. The two sawmills near Durango are ejidos, and the two sawmills near Oaxaca are comunales. All sawmills are members of the Forest Stewardship Council (FSC), a third-party organization that certifies sawmills that follow sustain-able forestry practices.

LogsPrivate trucking companies are contracted to haul harvested logs from the forest to the sawmills. Typical log lengths in the Durango area are 16 to 24 ft (4.9 to 7.3 m), which re-quires the use of logging trucks and trailers (Fig. 2). At the Oaxaca sawmills, logs are typically cut to a uniform

8-ft (2.4-m) length, which allows the use of flat-bed trucks (Fig. 3).

The raw material processed and the facilities at the four sawmills are summarized in Table 1. The majority of the

Figure 1—Durango and Oaxaca regions in Mexico.www.TrailMonkey.com

Figure 2—Specialized log-hauling semi-truck and trailer for carrying logs up to 24 ft (7.3 m) long.

General Technical Report FPL–GTR–167

2

Tabl

e 1—

Sum

mar

y of

saw

mill

cha

ract

eris

tics

Saw

mill

Sp

ecie

saLe

ngth

D

e-ba

rkin

g

P

rimar

y sa

win

g R

e-sa

win

g Lu

mbe

r gr

ades

A

ir

dr

ying

Ki

lndr

ying

Fi

nish

ed

prod

ucts

Dur

ango

#1b

P. d

uran

gens

is M

artín

ezP.

pon

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sa D

ougl

. P.

mic

hoac

ana

Mar

tínez

P.

ariz

onic

a E

ngel

m.

20–2

4 ft

(6.1

–7.3

m)

No

Band

saw

; 8,

16,

20

ft (2

.4,

4.9,

6.1

m)

lum

ber;

shor

t st

ock

Wan

e re

mov

al;

pa

llet s

tock

;1×

1×48

in.

(2.5

×2.5

×122

cm

) st

ock;

sla

ts fo

r fru

it bo

xes

No.

1N

o. 2

No.

3N

o. 4

No.

5

No

Oil-

base

d;

woo

d-fir

ed

kiln

Non

e

Dur

ango

#2

P. d

uran

gens

is M

artín

ezP.

coo

peri

Bla

nco

P. e

ngel

man

nii C

arr.

P. a

yaca

huite

Ehr

enb.

Q

uerc

us s

ider

oxyl

a H

umb.

& B

onpl

.Q

uerc

us ru

gosa

Née

16 ft

(4

.9 m

) Y

es

Ban

d sa

w;

8, 1

6 ft

(2, 4

.9 m

) lu

mbe

r; s

hort

stoc

k

Wan

e re

mov

al;

palle

t sto

ck;

1×1×

48 in

. (2

.5×2

.5×1

22 c

m)

stoc

k; s

lats

for f

ruit

boxe

s

No.

1N

o. 2

No.

3N

o. 4

No.

5

Yes

N

o ki

ln

Non

e

Oax

aca

#1

P. p

seud

ostro

bus

Lind

l. P.

pat

ula

Sch

lech

t. &

Cha

m.

P. o

axac

ana

Miro

v P.

lum

holtz

ii R

obin

s. &

Fer

n.

P. te

nuifo

lia B

enth

. P.

teoc

ote

Sch

lech

t. &

Cha

m.

P. le

ioph

ylla

Sch

lech

t. &

Cha

m.

P. o

ocar

pa S

chie

de

P. m

onte

zum

ae L

ambe

rt P.

prin

glei

Sha

w

P. d

ougl

asia

na M

artín

ez

P. a

yaca

huite

Ehr

enb.

Ab

ies

oaxa

cana

Mar

tínez

Que

rcus

laur

ina

Hum

b. &

Bon

pl.

8 ft

(2.4

m)

No

Band

saw

; 8

ft (2

.4 m

) lu

mbe

r; sh

ort

stoc

k

Wan

e re

mov

al;

palle

t sto

ck;

1×1×

48 in

. (2

.5×2

.5×1

22 c

m)

stoc

k

No.

1N

o. 2

No.

3N

o. 4

No.

5

Yes

(sho

rt te

rm)

Mod

ern

Non

e

Oax

aca

#2

P. p

atul

a S

chle

cht.

& C

ham

.P.

pse

udos

trobu

s Li

ndl.

8 ft

(2.4

m)

No

Band

saw

; 8

ft (2

.4 m

) lu

mbe

r; sh

ort s

tock

Wan

e re

mov

al;

palle

t sto

ck;

1×1×

48 in

. (2

.5×2

.5×1

22 c

m)

stoc

k

No.

1N

o. 2

No.

3N

o. 4

No.

5

Yes

(sho

rt te

rm)

Mod

ern

Doo

rs;

finge

r-jo

intin

g;m

oder

n

aP.

des

igna

tes

Pinu

s.b

A to

tal o

f sev

en s

peci

es a

re p

roce

ssed

; rep

rese

ntat

ive

spec

ies

are

liste

d he

re.

Lumber Processing in Selected Sawmills in Durango and Oaxaca, Mexico

3

logs are pine species, with a small percentage of oak. We saw no effort to separate the various species of pines at the log yards or during lumber processing. Pinus durangensis is the primary species processed at the Durango sawmills. About 60% of total production at Oaxaca sawmill #1 utilizes P. pseudostrobus and P. patula; 60% of production at Oaxa-ca sawmill #2 utilizes P. patula, with the rest consisting of P. pseudostrobus.

Log SortingLog shipments are unloaded in the log yard (Fig. 4); the logs are stacked into more orderly stockpiles by front-end load-ers (Fig. 5). All sawmills conduct some degree of log sort-ing, primarily by diameter. Durango sawmill #1 separates out all small-diameter, long, straight logs for utility poles, but does no additional sorting of the remaining logs (Fig. 6). Durango sawmill #2 separates all logs by diameter classes, so that more uniform diameters are processed in sawing. Small-diameter short logs are accumulated at all sawmills (Fig. 7) because no profitable markets currently exist for this resource. Neither of the Oaxaca mills sorts logs, and none of the sawmills sorts pine logs by species (Fig. 8).

Log BreakdownDurango sawmill #2 debarks logs prior to sawing (Fig. 9) so that the slab wood and edgings are bark-free. All four sawmills utilize large band saws (Fig. 10), and saw filers are in charge of daily maintenance of the blades. During the production of sawn lumber, all the sawmills try to maximize the production of wide lumber (Fig. 11), which is dictated by strong market demands in Mexico, although the widths attainable are limited by the log diameters. Production at all four sawmills is similar to the appearance-grade processing common in the United States for hardwood lumber, which typically processes random-width dimensions. In the United States, the majority of pine species are sawn into dimen-sion lumber for structural and utility applications, although some mills make an attempt to produce appearance-grade material. After the primary processing of full-width lumber,

Figure 3—Typical heavy-duty truck for transporting logs cut to nominal length of 8 ft (2.4 m).

Figure 4—Example of log unloading at sawmill.

Figure 5—Logs stacked in sawmill yard.

Figure 6—Example of sorting logs for specialty products; in this case, utility poles.

4

Figure 7—Accumulation of small-diameter logs at log yards resulting from lack of markets for small-dimension lumber.

Figure 8—Mixture of species and diameters of logs queued for sawing. Large-diameter log on right with heavy bark structure is Pinus pseudostrobus; other logs are P. patula.

Figure 9—De-barked logs.

Figure 10—Large band saw used at sawmills.

Figure 11—Sawmill processing in Mexico targets production of wide lumber because of strong market demands.


5

lumber with wane is edged through a gang-rip saw, resulting in narrower-width lumber. Slabs are accumulated and stock-piled (Fig. 12) for further reprocessing into smaller stock, such as slats.

Durango sawmill #2 and both Oaxaca sawmills process log-length lumber from logs that are harvested and cut to a specific length in the forest. Durango sawmill #2 primar-ily processes 16-ft (4.9-m) logs, and both Oaxaca sawmills primarily process 8-ft (2.4-m) logs. Durango sawmill #1 acquires the majority of their logs in 20- to 24-ft (6.1- to 7.3-m) lengths; a large percentage of these logs are later cut to 16-ft (4.9-m) lengths in the yard (Fig. 13). Only the high-est quality logs are processed full-length into lumber longer than 16 ft (4.9 m). This process results in an abundance of short log cut-offs (Fig. 14).

Slab RecoveryA common problem among all four sawmills is to find methods to utilize the sawmill waste. All sawmills have a re-saw production line (Fig. 15), where lumber is recovered from slabs. Three products are commonly processed on these re-saw lines (Fig. 16):

(a) Thin slats for fruit boxes (b) 1- by 1- by 48-in. (2.5- by 2.5- by 122-cm) clear stock for broom handles(c) Components for pallet stock

All four sawmills named these three products as outlets for lumber recovered from slabs. No other primary products are made from slabs.

GradingAll sawmills have similar grading methods and grading sys-tems. Green lumber is visually graded and categorized into one of five lumber grades, No. 1 through No. 5. The No. 1 and No. 2 lumber grades are commonly combined into a single high grade, referred to as “Firsts.” Table 2

Figure 12—Example of slabs accumulated at sawmills.

Figure 13—Bucking long logs into short lengths in log yard.

Figure 14—Large quantity of log shorts resulting from poor log bucking practices.

Figure 15—Lumber recovered from slabs is sawn into slats, pallet stock, and blanks for broom handles.


6

Figure 16—Byproducts made from slabs: (a) slats for fruit boxes; (b) blanks for broom handles; (c) pallet components.

Table 2—Summary of lumber grade specifications, based on interviews with lumber graders Grade Knot size Frequency and characteristics of knots and other defects No. 1 No knots Clear both faces

No. 2 Smaller than 1 in. (2.5 cm) Clear one face; 4 or fewer knots permitted on back

No. 3 Smaller than 2 in. (5 cm) 4 or fewer knots permitted on both faces

No. 4 Smaller than 2 in. (5 cm) 5 to 8 knots permitted on both faces

No. 5 Larger than 2 in. (5 cm) More than 4 knots on both faces; checks, splits, and centered pith


7

summarizes the specifications of the lumber grades, based on our discussions with the graders. This grading system is applied only to full-length lumber, and no grading manual was available at any of the sawmills. Figure 17 shows repre-sentative boards from each of these lumber grades.

Kiln-DryingThree of the four sawmills operate dry kilns. Durango saw-mill #2 does not operate a kiln; 100% of their product is sold as green or air-dried lumber. Durango sawmill #1 oper-ates an oil kiln that is heated by burning solid wood waste. Three shifts are required to manage this kiln; highly skilled operators are required to maintain proper temperature and humidity control. Both Oaxaca sawmills operate modern kilns (Fig. 18) with computer-controlled sensors and utilize sawdust waste for heat generation. At three of the four saw-mills, we observed stickers that were improperly aligned

(Fig. 19). Only Oaxaca sawmill #2 had perfectly aligned stickers in every lumber bundle that we inspected.

Finished ProductsWith the exception of thin slats, pallet lumber, and broom-stick handle blanks, only Oaxaca sawmill #2 manufactures secondary products; their primary added-value product is floating-panel doors (Fig. 20). This sawmill is in the process of installing a finger-jointing system to be able to efficiently utilize the short clear lumber from mill residues (Fig. 21).Although Oaxaca sawmill #2 is using modern equipment to produce fine quality doors, we saw a few instances of splits and checks in the rails and stiles of these manufactured products (Fig. 22). We noticed that the rails and stiles in the finished doors are primarily made from flat-sawn lumber, and they are stored in the warehouse in an unfinished con-dition. To produce a more dimensionally stable and value-added product, we recommended that the sawmill consider

Figure 17—Representative boards from lumber grades: (a) “Firsts”: combination of No. 1 and No. 2 grade lumber; (b) No. 3 grade; (c) No. 4 grade; (d) No. 5 grade. See Table 2 for description of grades.


8

quarter-sawn lumber for door rails and stiles. Because the operation is a sawmill, specially cut lumber can be selected from the production line. In addition to the use of more di-mensionally stable lumber, we also recommended the appli-cation of a surface finish soon after manufacture, to reduce the amount of shrinking and swelling resulting from fluctua-tions in relative humidity. We recommended that lumber for the unfinished door market be immediately shrink-wrapped before storage.

Figure 18—Example of modern drying kiln for Oaxaca sawmill.

Figure 19—Misaligned stickers during drying result in warped lumber.

Figure 20—Floating-panel, solid-wood doors manufac-tured in Oaxaca.

Figure 21—Modern finger-jointing system.

Figure 22—End checking on flat-sawn grain of unfinished door stiles.


9

Information GatheredWith our newly gained knowledge of the pine species avail-able in Oaxaca and Durango as well as the lumber process-ing and grading capabilities, we conducted a review of the literature to compare the mechanical properties of the pine species utilized in these regions in Mexico to those com-monly utilized in the United States.

Comparison of Mexican and U.S. PinesFigure 23 compares the specific gravity of several U.S. and Mexican pine species. Table 3 compares the modulus of rupture (MOR), modulus of elasticity (MOE), side hardness, and radial, tangential, and volumetric shrinkage of four na-tive commercial pines of the United States, one species (P. radiata) that is native to the United States but has com-mercial value only as a plantation species in foreign coun-tries, and three Mexican pines. Of the commercial U.S. spe-cies, P. taeda is a southern yellow pine, P. ponderosa and

P. contorta are western yellow pines, and P. strobus is northern white pine. Pinus radiata is native to California and Guadalupe Island. Pinus taeda has the highest specific gravity of all the species shown in Figure 23 and is con-sidered one of the strongest softwood species in the United States for structural applications. Southern yellow pine is commonly used for structural joists and planks and in engi-neered wood products such as glued-laminated timber mem-bers. Pinus ponderosa and P. contorta are commonly classi-fied as Western Woods in U.S. lumber grades. These species are known to possess lesser mechanical properties compared with those of southern yellow pine. These species are com-monly used for construction studs as well as nonstructural applications in molding and millwork. Pinus strobus is usually processed as appearance grade lumber and used in nonstructural applications such as furniture, molding, and millwork.

The processing of Mexican pines that we observed at the four sawmills most closely resembles the U.S. grade sawing methods for P. strobus. As observed in Figure 23, the specif-ic gravity of the Mexican pines exceeds the specific gravity of P. ponderosa, P. contorta, P. radiata, and P. strobus. Our data indicate that Mexican pines have sufficient to excellent mechanical properties for structural and semi-structural applications.

Comparison of Mexican and U.S. OaksTable 4 compares the MOR, MOE, side hardness, and ra-dial, tangential, and volumetric shrinkage of three native oaks of the United States and six species of Mexican oaks. Quercus alba is the most valuable white oak in the United States, and Q. rubra is the most valuable red oak. Quercus virginiana is much less valuable than these two species (per-haps because of its small size, poor form on many sites, and drying difficulties), and it resembles the Mexican oaks in

Figure 23—Specific gravity of various U.S. and Mexican pine species.


Table 3—Physical properties and dry (12% moisture content) properties of pine (Pinus) species Shrinkage, green to ovendry (%)

Data sourceaBasic specific

gravity Species MOR(MPa)

MOE(GPa)

Side hardness(kN) Radial Tangential Volumetric Originb

FPL 0.34 P. strobus 59 8.5 1.7 2.1 6.1 8.2 USA 0.47 P. taeda 88 12.3 3.1 4.8 7.4 12.3 USA 0.38 P. contorta 65 9.2 2.1 4.3 6.7 11.1 USA 0.42 P. ponderosa 65 8.9 2.0 3.9 6.2 9.7 USA 0.46 P. radiata 81 10.2 3.3 — — — Asia Cockrell 0.46 P. radiata 91 12.4 3.4 5.2 7.0 11.4 CA 0.41 P. radiata 79 10.0 3.2 4.0 6.3 — AustraliaLavers 0.43 P. radiata 85 9.0 3.8 — — — Kenya 0.39 P. radiata 85 8.3 2.7 — — — NZ Davalos 0.46 P. durangensis 102 11.9 3.4 — — 13.1 Mexico 0.47 P. patula 95 12.5 3.8 — — 10.8 Mexico Sachsse 0.45 P. pseudostrobus — 11.1 — — — 11.6 Mexico aFPL 1999b; Cockrell 1959; Lavers 1983; Davalos and others 1978; Sachsse and Cruz de León 1992. bCA is California; NZ, New Zealand.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

P. taed

a

P. pon

deros

a

P. con

torta

P. radia

ta

P. stro

bus

P. pse

udos

trobu

s

P. patu

la

P. dura

ngen

sis

Spec

ific

grav

ityU.S. pines Mexican pines

10

anatomy. Quercus alba and Q. rubra are both ring-porous species; Q. virginiana is diffuse-porous, as are the many of the Mexican oaks. The mechanical properties of the Mexi-can oaks are largely unknown, but shrinkage is high, which may partially account for the limited utilization of this wood.

Comments and RecommendationsThe following comments and recommendations are based on our review of practices observed at the sawmills in Oaxa-ca and Durango:

• More efficient timber harvesting—specifically, bucking logs to desired lengths—should be conducted in the for-est such that logs arrive at the sawmill in lengths that will be processed into lumber. Hauling 20- to 24-ft- (6.1- to 7.3-m-) long logs is not cost-effective when the final length of lumber is typically 16 ft (4.9 m) and shorter, and it results in significant waste.

• Lumber yield and sawing efficiency can be improved if logs are initially sorted by diameter in the log yard. Pro-cessing of logs with a wide range of diameters reduces efficiency because it multiplies the number of decisions the sawmill operator must make to maximize grade yield.

• Debarking of logs at the sawmill should be considered for several reasons. In the case of utility poles, the re-moval of bark accelerates drying and facilitates treat-ment with chemicals. Removal of bark has advantages for sawing: defects are visible (Koch 1985), and cutting bark-free logs extends the service life of saws. Sawmills can sell log residue to pulpmills as a value-added product if the bark is removed. De-barking of logs before storage in the log yard accelerates drying and results in a higher-valued product (Simpson and Wang 2003). Harkin and Rowe (1971) described the properties of bark and dis-cussed its possible uses, such as for mulch.

• The structural pole market and rustic round-timber furni-ture market are likely outlets for small-diameter logs.

• In log breakdown, greater care to reduce non-uniformity in thickness would produce higher-valued lumber.

• Recovering material from slabs is an important process in the complete utilization of the timber resource. Prod-ucts currently being recovered from slabs are fruit box slats, broomhandle blanks, and pallet stock. Although the market for these products seems to be well estab-lished, we recommend that other higher-valued uses for this resource be researched. In the United States, a wide range of products in the molding and millwork industry are produced from narrow stock, such as trim, picture frames, lattice, and finger-jointed molding. We recommend that the sawmills review the information on producing higher-valued products that is available from trade associations, such as the Wood Moulding and Mill-wood Producers Association (www.wmmpa.com).

• Utilization of narrow and short lumber resources could be extended by the use of finger-jointing. Finger-jointed molding and millwork products are common in the Unit-ed States, and initial steps should be taken to make these products acceptable in Mexico. Establishing a finger-joint production line requires knowledge of processing and expected performance. Historical information is available from the Forest Products Laboratory (Jokerst 1981).

• Lumber drying is an important aspect of the production of wood products. For sawmills that are not currently set up to kiln dry lumber, steps should be taken to imple-ment proper air-drying techniques. Research information is available from the Forest Products Laboratory (FPL 1999a, Peck 1956, Tschernitz and Simpson 1985).

• Quality control in lumber stacking and stickering should be implemented. The Forest Products Laboratory pub-lishes information on the importance of proper lumber


Table 4. Physical properties and dry (12% moisture content) properties of oak (Quercus) species Shrinkage, green to ovendry (%)

Datasourcea

Basic specific gravity Species

MOR(MPa)

MOE(GPa)

Side hardness(kN) Radial Tangential Volumetric Origin

FPL 0.56 Q. alba 99 12.5 5.7 5.6 10.5 16.3 USA 0.60 Q. rubra 105 12.3 6.0 4.0 8.6 13.7 USA 0.80 Q. virginiana 127 13.7 — 6.6 9.5 14.7 USA Cruz 0.59 Q. affinis — — — 4.6 12.9 18.5 Mexico 0.73 Q. rysophylla — — — 5.0 11.5 17.5 Mexico 0.75 Q. polymorpha — — — 5.4 11.4 17.9 Mexico 0.74 Q. prinopsis — — — 6.2 13.2 20.8 Mexico Echenique 0.68 Q. barvinervis — — — — — 21.2 Mexico Kukachka 0.91 Q. oleoides 79 12.4 8.9 — — — Tropical America aFPL 1999b; Cruz de Leon 1994; Echenique Manrique and Becerra Martínez 1969; Kukachka 1970.

11

stickering for kiln-drying and the effects of improper stickering (Simpson 1991).

• We found no value-added outlet for No. 5 lumber, the lowest grade produced at the sawmills (Table 2). We recommend that value-added outlets be considered for the utilization of this material; one possibility is the pulp chip market. Other alternatives are (1) to re-saw the lower grade stock into short clear lumber and use fin-ger-jointing and (2) to produce rustic end-use products, which are not downgraded by the presence of knots and other defects. Examples of rustic uses of lower-grade lumber in value-added products are shown in the Appendix. The round-timber members used in some of these structures were likely de-barked and then dried to a target moisture content.

• For sawmills that plan to implement industrial molders, oak presents a tremendous opportunity for process-ing flooring and other products, such as furniture and cabinets. In the few instances that we observed oak be-ing processed, the final product was pallet stock. In the United States, oak is the predominant species used for furniture and wood flooring products. It is an excellent species for wood flooring because of its high specific gravity. We found research articles relating to utilization of oak species in a literature search of the Mexican jour-nal Madera y Bosques.

• Finally, if sawmills wish to export their lumber products to the United States in the future, the operators will need a good understanding of U.S. lumber processing and grading systems. The introduction of structural lumber will require approval by U.S. grading agencies. Informa-tion about the U.S. process of acceptance of structural

lumber products was reported by Green and Hernandez (2000). Some Mexican pine species have already been accepted in the United States for use as semi-structural products, such as decking. Table 5 shows Mexican pine species accepted by the Board of Review of the Ameri-can Lumber Standards Committee (www.alsc.org). With proper processing equipment, Mexican sawmills can cur-rently produce for export radius-edge decking and exte-rior decking to the dimensions used in the United States.

Trade Associations Information on the process and dimensions required for producing quality oak flooring or other products is available from the following trade associations:

National Wood Flooring Association, www.woodfloors.org/consumer

Wood Flooring Manufacturers Association, www.nofma.org

Railway Tie Association,www.rta.org

Literature CitedCockrell, R.A. 1959. Mechanical properties of California-grown Monterey pine. Hilgardia 28:227–228.

Cruz de Leon, J. 1994. Nota sobre las características físicas de la madera de cuatro especies de Quercus de Nuevo Leon, México. Investigación Agraria, Sistemas y Recursos Fores-tales 3:91–101.

Davalos, S.R.; R. Echenique Manrique; V.J. Sánchez, 1978. Características mecánicas de tres especies de pino del Cofre de Perote, Veracruz. Biótica 3:37–55.

Table 5—Mexican species approved by board of review for decking applications

Mexican pine species Approval limited to specific areaa

Approval obtaineda Product

Grade stamp nomenclature

Supportingagencyb

Radius edge decking 24-in. (608-mm) span Michoacan and adjacent States

Exterior decking 16-in. (406-mm) span

Mex. Pine (I) MCH RRA/WCLIB

Radius edge decking 24-in. (608-mm) span for 5/4 by 6/4 in. (31.8 by 38 mm) 16-in. (406-mm) span for 5/4 by 4/4 in. (31.8 by 25.4 mm)

P. strobiformis, ayacahuite, leiophylla, chihuahuana,lumholtzii, arizonica, engelmannii,durangensis, jeffreyi, cooperi, montezumae, douglasiana, rudis, hariwegii, michoacana, pseudostrobus,maximinoi, oaxacana, nubicola, patula, oocarpa, pringlei, teocote, lawsoni, herrerai

Durango and Chihuahua

Exterior decking 24-in. (608-mm) span for 5/4 by 6/4 in. (31.8 by 38 mm) 16-in. (406-mm) span for 5/4 by 4/4 in. (31.8 by 25.4 mm)

Mex. Pine (I) DUR RRA/WCLIB

a Includes all species of Mexican pine except P. strobiformis and P. ayacahuite.b RRA is Renewable Resource Associates; WCLIB, West Coast Lumber Inspection Bureau.


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Echenique Manrique, R.; J. Becerra Martínez. 1969. Algu-nas características físico-mecánicas de la madera de tres es-pecies de la cordillera neo-volcánica. Notas Técnicas 6:1–6.

FPL. 1999a. Air drying of lumber. Gen. Tech. Rep. FPL–GTR–117. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

FPL 1999b. Wood handbook. Wood as an engineering mate-rial. Gen. Tech. Rep. FPL–GTR–113. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI.

Green, D.W.; R. Hernandez. 2000. Codes and standards for structural wood products and their use in the United States. In: Proceedings of Forest Products Study Group Workshop, North American Forestry Commission, Merida, Yucatan, Mexico. www.fpl.fs.fed.us/documnts/pdf2000/green00d.pdf

Harkin, J.M.; J.W. Rowe. 1971. Bark and its possible uses. Res. Note FPL–RN–091. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplrn/fplrn091.pdf

Jokerst, R.W. 1981. Finger-jointed wood products. Res. Pap. FPL–RP–382. U.S. Department of Agriculture, Forest Ser-vice, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplrp/fplrp382.pdf

Koch, P. 1985. Utilization of hardwoods growing on south-ern pine sites. Agric. Hbk. No. 605. U.S. Department of Ag-riculture, Forest Service, Washington, DC.

Kukachka, B.F. 1970. Properties of imported tropical woods. Research Paper FPL–RP–125. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI.

Lavers, G.M. 1983. The strength properties of timber. Build-ing Research Establishment Report. London. 60 pp.

Peck, E.C. 1956. The air drying of lumber. FPL Rep. No. 1657. U.S. Department of Agriculture, Forest Service, For-est Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplmisc/rpt1657.pdf

Sachsse, H.; J. Cruz de León. 1992. Das holz de mexi-kanischen Pinus pseudostrobus Lindl. Holz als Roh-u. Werkstoff 50:29–32

Simpson, W.T. 1991. Dry kiln operator’s manual. Agric. Hbk. AH–188. U.S. Department of Agriculture, Forest Ser-vice, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/usda/ah188/chapter05.pdf

Simpson, W.T.; X. Wang. 2003. Estimating air-drying times of small-diameter ponderosa pine and Douglas-fir logs. Re-search Paper FPL–RP–613. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplrp/fplrp613.pdf

Tschernitz, J.L.; W.T. Simpson. 1985. FPL design for lum-ber dry kiln using solar/wood energy in tropical latitudes. Gen. Tech. Rep. FPL–GTR–44. U.S. Department of Agricul-ture, Forest Service, Forest Products Laboratory, Madison, WI. www.fpl.fs.fed.us/documnts/fplgtr/fplgtr44.pdf

Appendix—Uses for Low-Grade LumberThe following figures illustrate uses for low-grade lumber in value-added products. The round-timber members used in some of these structures were likely de-barked and then dried to a target moisture content.

Rustic semi-structural application.

Semi-structural application.


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Rustic furniture.


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Structural application for round timbers.Non-structural application.

Semi-structural application.


Documents

Lumber Processing inLumber Processing in Selected Sawmills in Durango and Oaxaca, Mexico 3 logs are pine species, with a small percentage of oak. We saw no effort to separate the various